There are many reasons to use solar panels to power your home. Because of advanced technology and efficiency, solar equipment costs have reduced a lot in the last decade. Solar kits are affordable for majority of people.
Off-grid life is attractive for many reasons. Maybe public grid is not available in your area, or electricity is too expensive. Regardless of the reason you are off the grid, the first step in determining the best off-grid solar system is to determine the power required for production and storage.
What is the off-grid system?
The whole system includes solar panels, solar recharge controller, off grid inverter, gel battery etc.
1. Sun shines on the solar panels generating DC electricity
2. The DC electricity is fed into a regulator which controls the amount of charge
3. Batteries are charged
4. 12 volt appliances can be run directly off the batteries or the current routed through an inverter which converts it to AC electricity; suitable for running standard home appliances.
Even if you know how this system works but how to design the system?
A client from south of Portugal needs a solar system for his house. He calculated the power and electricity consumption of his home appliance in the house.
Power labels are available on all home appliances. That being the case, you should be able to get all the information you need from the tag. Some list wattage, some list the voltage range, some list amps, and some list the dc voltage and amps used to convert the ac voltage to dc power blocks.
Volts x Amps = Watts
Watts x (hours a day) = daily W hours
Some loads such as refrigerators, air conditioners, cannot be turned on continuously, and high surges are generated when the compressor is turned on, which makes it difficult to determine how much accumulated power or watt hours are used in a day.
If you receive an energy star rating, you can find the Energy Star label on your device. The energy star label tells you the average kilowatt hour used per year.
From there, you can simply divide it by the number of days in the years
kWh a year / 365 days = kWh a day
Here is his home appliance power list.
Total Electricity Consumption=22480wh=22.48kwh
These projects are mainly distributed in Faro, the south of Portugal.
According to average sun insolation here every month, 1KW solar panel can produce about 4.5KWH electricity a day
22.48/4.5=4.99KW solar panels
Therefore, to power home appliance every day, totally 5kw solar panels are required.
In Faro, there is good sunshine all year round, especially in hot summer days. We assume battery supply electricity to home appliance for one day.
Batteries capacity is AH, Battery Voltage is 12V
Total electricity consumption=22480WH=22480VAH
Total battery capacity = 22480/12=1873AH
If battery is 250AH each, it needs 1873/250=7.49 pieces battery
By taking some margin you can select 8*250AH deep cycle GEL battery.
5KW system is rated at 96V, so the charge controller is also 96V.
Current = Power output of Panels / Voltage = 5000W/96V = 50 A
The controller needs to be 96V50A
Off Grid Inverter
Total power of inverter=peak load of home appliance=2000W
But when air conditioner is starting-up, instantaneous power is very large, about 3 times of the output power (750w*3), At that moment, total power may be up to 4900w. For safety of whole system, it is better to choose a 5kw inverter.
In a short word, even if the clients do not know how big the system that they need, we also can design whole system according to customer request.
When we know total KWH that a household need to use a day, we can calculate the size of solar panels, batteries, inverter and solar recharge controller etc.
For this client, a 5KW off grid solar power system is enough, equipped with a 96V50A controller, a 5kw inverter and 8*12V250AH GEL battery.